Floor Jack Overload Valve Theory

[alton]

Does anyone know how the fluid is supposed to flow in the overload valve? I removed the top screw and was expecting to see the bottom screw so I could screw it in and count the number of turns. All I saw was fluid filling the hole and what looked like a slolid piece of rubber or something covering what I expect to be the bottom screw. Figured I better stop there and ask here before I continued. Does the overload valve pass fluid only when it goes into overload mode? Thanks, Alton.

 

[Jeeper]

The overload is essentially a check valve but it isn't used as a one way flow control. Think of a ball that sits in a cone with then fluid coming from the small part of the cone. In this case there is a heavy spring that is in contact with the adjusting cap and forces the spring down on the ball. When fluid presses against the ball when the jack is under load the ball wants to move away from the cone it the spring tension keeps it against the cone. If the fluid pressure is high enough it will compress the spring and allow the ball away from the cone, allowing fluid through and relieving pressure.


What kind of jack is it?

 

[Hiball]

Does anyone know how the fluid is supposed to flow in the overload valve? I removed the top screw and was expecting to see the bottom screw so I could screw it in and count the number of turns. All I saw was fluid filling the hole and what looked like a slolid piece of rubber or something covering what I expect to be the bottom screw. Figured I better stop there and ask here before I continued. Does the overload valve pass fluid only when it goes into overload mode? Thanks, Alton.

What type of Jack? Some Jacks used a Piston Cup to Cover the Overload Galley that sits above the Adjustment,.

Its Not Uncommon to see a little bit of Oil rest above the Overload, <-- Even on a Properly adjusted Overload. This is why you see Manufactures use such seals (above) or Freeze plugs or Caps with Orings. Now back to your Question, The Overload only opens when the Cylinder PSI exceeds the Seat/Ball/Spring Pressure set by the Overload adjustment. Just because your seeing a little oil on top of your Adjustment, Doesn't necessarily mean its Improperly set. As your lifting a load, The PSI increases, When you get to a certain point, the Amount (volume) of Oil that is transferred from pump piston to cylinder "when" at Max Load is reduced to comply with the Seals Max PSI.

 

[basspro]

Hiball and Jeeper are both correct. One way to check a jack would be to set it in a hydraulic press and put the rated pressure on the jack with the jack at near full stroke, leave under pressure overnite. If the press has a guage you will know the next day where its leaking and if it is holding correctly. You may not have access to a press, but often enough you can mount your jack in a vise, find the exact same size ball that sits below the adjustment screw. Get ahold of a good hard punch roughly the same size diameter as the ball, and a ball peen hammer of choice. Give the ball 1-2 good hits, what this does is it reformes the sealing surface (seat) where the ball sits. Insert a new ball and a new spring, you should be good to go. Hope this helps.

 

[Hiball]

To the OP..

"IF" the seat does need reworked, please use a punch aprox the same diameter of the galley, overload balls are very small in comparison to galley size and you "greatly" increase your chance of slipping off the small ball and damaging the seat or the area around it with a small punch. Would also recommend light hits initially, inspect and repeat as necessarily. It's very easy to overseat a overload seat..

 

[alton]

Hiball, it is an older Sears. ,model 328.12002, 1 1/2 ton floor jack.

 

[Hiball]

Hiball, it is an older Sears. ,model 328.12002, 1 1/2 ton floor jack.

According to my notes, it does utilize a piece of rubber packing above the adjustment to help seal the cap, also uses a "cone style" overload versus the ball style.

 

[alton]

Thanks Hiball. When that seat opens, where does the fluid go? No ball, huh. I would have been looking forever. You are a champ.

 

[Hiball]

Thanks Hiball. When that seat opens, where does the fluid go? No ball, huh. I would have been looking forever. You are a champ.

It bypasses back into the reservoir, according to what I have wrote down for kit components, no ball on the overload.

 

[alton]

Thanks again Hiball. The fluid I saw in the galley was above the piston cup. It filled the galley to the top. Must have taken a lot of pressure to get up there. Also, I take it there is another passageway machined in the galley for the fluid to return to the reservoir when it breaches the conical seat. Just trying to square this away in my old geezer brain. Alton.

 

[Hiball]

Thanks again Hiball. The fluid I saw in the galley was above the piston cup. It filled the galley to the top. Must have taken a lot of pressure to get up there. Also, I take it there is another passageway machined in the galley for the fluid to return to the reservoir when it breaches the conical seat. Just trying to square this away in my old geezer brain. Alton.

When the overload lifts the oil is under pressure, the return vein is fairly small thus some oil makes it way above the adjusting plug, I've always assumed the reason the oil never seaped back into the reservoir is because the reservoir oil pressure is greater than the oil in the overload galley.

Again.. Very common to see signs of oil in the overload..

 

[alton]

Hiball, that makes sense to me, but today I really have a bit of the curious. Out of sheer boredom and an inquisitive mind, i went outside to the jack, removed the upper screw from the Overload Galley and removed the excess oil from atop the rubber plug. I turned the handle to open the release valve and proceeded to pump away. Lo and behold if fluid didn't rise above the rubber plug again. What possible pressure pushed the fluid up like that? Smoke coming out of my ears. Houston, we have a problem. I decided to bleed it again so with the release valve open, the cradle down and the reservoid topped off, I began pumping. Fluid would overflow from the fill hole every now and then but the cradle lifted to its highest point. I put the fill hole plug back in, thinking the reservoir might need it for proper operation and it danced around as I pumped. I held it down with my finger and when released it spit a lot of air at me. It did this twice and then stopped. I topped off the reservoir once again and pumped a few more times without any oil appearing above the rubber plug atop the Overload Galley. Put the top screw back in, closed the release valve and raised the cradle all the way up. The cradle lowered itself very, very slowly. I have nobody around to remove the jack from my work table so I do not know if it will lift a load. Maybe one of my 3 sons will stop by one day and help me or I will just have to wait for my back to get better. Hope this book allows you enough info to give me some more good ideas as to what is going on with this jack. Thanks, Alton.

 

[Hiball]

Hiball, that makes sense to me, but today I really have a bit of the curious. Out of sheer boredom and an inquisitive mind, i went outside to the jack, removed the upper screw from the Overload Galley and removed the excess oil from atop the rubber plug. I turned the handle to open the release valve and proceeded to pump away. Lo and behold if fluid didn't rise above the rubber plug again. What possible pressure pushed the fluid up like that? Smoke coming out of my ears. Houston, we have a problem. I decided to bleed it again so with the release valve open, the cradle down and the reservoid topped off, I began pumping. Fluid would overflow from the fill hole every now and then but the cradle lifted to its highest point. I put the fill hole plug back in, thinking the reservoir might need it for proper operation and it danced around as I pumped. I held it down with my finger and when released it spit a lot of air at me. It did this twice and then stopped. I topped off the reservoir once again and pumped a few more times without any oil appearing above the rubber plug atop the Overload Galley. Put the top screw back in, closed the release valve and raised the cradle all the way up. The cradle lowered itself very, very slowly. I have nobody around to remove the jack from my work table so I do not know if it will lift a load. Maybe one of my 3 sons will stop by one day and help me or I will just have to wait for my back to get better. Hope this book allows you enough info to give me some more good ideas as to what is going on with this jack. Thanks, Alton.

1st off.. "Dont Top off the Reservoir" there needs to be Head space in the Reservoir to accomidate the Space needed when the Oil returns. The Oil should Rest just above in the Inner cylinder when peering through the hole.

2ndly.. And im trying to follow you here.. Did you just remove the Upper cover on the Reservoir or the "Lower" adjusting Plug? If your getting oil above the Lower plug with "NO LOAD", You need to check the Overload setting by tightening it down to completely Closed from its current setting. It should rest somewhere between 1-2 revolutions out. Of course.. All these settings are dependent on the Spring tension and it being in Good condition (I have seen them in 2 pieces)

This is a Very simple Designed Jack, First Address the Oil level, Then report back on the Overload setting.

 

[alton]

1st off.. "Dont Top off the Reservoir" there needs to be Head space in the Reservoir to accomidate the Space needed when the Oil returns. The Oil should Rest just above in the Inner cylinder when peering through the hole.

2ndly.. And im trying to follow you here.. Did you just remove the Upper cover on the Reservoir or the "Lower" adjusting Plug? If your getting oil above the Lower plug with "NO LOAD", You need to check the Overload setting by tightening it down to completely Closed from its current setting. It should rest somewhere between 1-2 revolutions out. Of course.. All these settings are dependent on the Spring tension and it being in Good condition (I have seen them in 2 pieces)

This is a Very simple Designed Jack, First Address the Oil level, Then report back on the Overload setting.

The oil is just above the cylinder. I only removed the upper cover. I could only see the rubber cap above the lower adjusting screw. As I removed the upper cover this time, oil just kept rising and gushing out.??? I opened the release valve and removed the oil fill hole plug which stopped the oil from coming out of the Overload Galley. I was calling the large cylinder that the fill hole plug goes in, the reservoir. You must be calling the Overload Galley, the reservoir. I removed the rubber cap, not cup, from above the adjusting screw and bottomed the screw out at approx. 2 1/8 turns. That is my latest report. Thanks.

 

[Hiball]

The oil is just above the cylinder. I only removed the upper cover. I could only see the rubber cap above the lower adjusting screw. As I removed the upper cover this time, oil just kept rising and gushing out.??? I opened the release valve and removed the oil fill hole plug which stopped the oil from coming out of the Overload Galley. I was calling the large cylinder that the fill hole plug goes in, the reservoir. You must be calling the Overload Galley, the reservoir. I removed the rubber cap, not cup, from above the adjusting screw and bottomed the screw out at approx. 2 1/8 turns. That is my latest report. Thanks.

Fill hole = Reservoir

I'm calling the "overload galley" the space below the cap and the bottom of the overload valve.

2 1/8 turns? Tough to tell without having here on the Test station, but I'd be willing to bet that's a bit light with the current spring.

 

[alton]

I'll try it at 1 1/2 turns. Thanks again.